In the field of optical parts, information recording medium, and biotechnology-related parts, a minute shape is required to be molded on a member in recent years. To meet this requirement, efforts have been made to develop a technique of producing a molding material having a minute shape formed thereon, wherein pressure is applied to a die having minute shape formed thereon, and the minute shape is transferred onto the resin molding material.
Generally, in the resin molding process using a molding device equipped with the aforementioned die, difficulties will occur in the molding releasing operation if the mold releasing force in the mold releasing step of releasing the molding material from the die is greater than predetermined mold releasing force. This may damage the molding material. Especially in the case of a molding device based on nano-imprinting method (also called the nano-imprinting device) wherein a minute shape is transferred onto the resin and molding operation is performed, using the die (also called a mold or a stamper) with a minute shape formed thereon, the minute shape transferred onto the molding material will be more susceptible to damages if the mold releasing force is greater.
In this case, the aforementioned predetermined mold releasing force differs for each molding material according to the type of the resin, the size and shape of the molding material, molding conditions and other factors.
Thus, to improve the mold release characteristics, the surface of the die is generally coated with a mold release agent. The mold release agent is subjected to deterioration with the multiple times of molding operations, and the release characteristics are reduced. Thus, if there is an increase in the mold releasing force, and the mold releasing force has increased over a predetermined level, the molding material and die will be more susceptible to damage, as described above. Particularly, the portion of minute shape will be vulnerable to damage.
FIG. 12 shows the result of measuring the changes in the mold releasing force resulting from the number of shots for a certain product (product A). In this example, if the mold releasing force has exceeded 0.40N, the minute shape transferred onto the molding material will be damaged. In the following description, the aforementioned predetermined mold releasing force that causes the minute shape to start being damaged will be called critical mold releasing force.
Under the circumferences described above, the management of the mold releasing force and maintenance of the die are very important.
Regarding the maintenance of the die, a die management apparatus has been proposed, wherein the time of die maintenance including the time of die replacement is indicated through management of the number of molding shots (Patent Document 1 for example).
According to another proposal, the die maintenance including the die replacement is managed wherein the period when die maintenance is required based on the number of molding shots is added to the period when maintenance is required based on the time elapsed after the previous maintenance (Patent Document 2 for example).
Patent Document 1: Unexamined Japanese Patent Application Publication No. Hei 3-124417
Patent Document 2: Unexamined Japanese Patent Application Publication No. Hei 5-345343